The Wilwood FSLI4 (part 120-11133-RD) is a four-piston forged aluminum caliper from the Forged Superlite Internal line, with stainless steel pistons at a 1.62in bore and a 1.25in rotor width. The manufacturer says each body is stress-flow forged so the metal grain follows the caliper contour, which is the main structural reason to choose it over a cast or machined-block caliper. Internal fluid ports replace the external crossover tubes used on older Superlite calipers, so there is no exposed hard line or cross-over tube to damage at the track. At 5.2 lb, it is built for race use where stiffness and fade resistance matter more than street comfort.
Fitment is universal, with a lug mount and a 3.50in mount center, and the manufacturer lists a maximum rotor diameter of 13.06in. Because this is not a vehicle-specific part, confirm bracket clearance, hub pattern, and rotor size before ordering. Installation suits an experienced DIY mechanic. The manufacturer's Superlite-series install sheets call for torquing bracket bolts to 60 ft-lb with red thread locker and removing the center bridge pad retainer to load pads. They also specify bleeding the farthest caliper first and using Wilwood Hi-Temp 570 or higher fluid, or EXP 600 Plus for severe braking.
The manufacturer states that the FSLI4 design uses two additional bleed screw assemblies in place of a transfer tube, which allows right- and left-hand calipers to be mounted in either a leading or trailing position.
The manufacturer describes internal fluid ports that eliminate the external fluid cross-over tubes, along with the risk of a damaged tube.
The manufacturer's Superlite-series install sheets recommend Wilwood Hi-Temp 570 grade fluid or higher, and Wilwood EXP 600 Plus Racing Brake Fluid for severe braking or sustained high-heat use.
The manufacturer advises that installation be done by people experienced with disc brake systems. Plan on a torque wrench, red thread locker, and a brake bleeding setup. Torque the bracket bolts to 60 ft-lb one at a time, then check that the pad top sits flush with the rotor outside diameter. Bleed the caliper farthest from the master cylinder first, then check the system for leaks. Test the pedal before driving, and re-bed the pads per the manufacturer's procedure.
